Effect of very early age exposure on chloride ingress and service life performance of binary and ternary concretes

Abstract

The positive effects of supplementary cementitious materials in increasing chloride resistance of concrete under normal ages of exposure have been well established. However, little information is available on their performance under very early age exposure conditions. In the work reported, the performance of binary and ternary mixes incorporating silica fume and fly ash, with regards to time variations of chloride diffusion parameters and their effects on service life predictions, under very age exposure conditions was investigated. The results showed that for moderate cover depths, the effect of very early age exposure in reducing service life was considerable for all the mixes studied. This effect was however more significant for the binary mix containing 30% fly ash (FA30), which for a cover depth of 50 mmm, showed a 30% reduction in service life compared to the exposure age of 28 days. The corresponding values for the binary mix with 10% silica fume (SF10) and the ternary mix with 5% silica fume and 15% fly ash (SF5FA15), were 14% and 19% respectively. With increasing depth of cover, the adverse effect of early age exposure diminished and for a cover depth of 90 mm, the reduction in service life amounted to 7%, 3%, and 5% for the FA30, SF10, and SF5FA15 mixes respectively.